The invention relates to a ratchet assembly for a surgical instrument, more particularly to a ratchet assembly allowing alternating two-directional ratcheting with enhanced reliability and less unengaged motion during changeover from ratchet in one direction to the other.
Ratchet devices are known for use in surgical instruments for allowing incremental movement or pivot, for example of a trigger member, through a stroke in one direction followed by changeover to ratchet along a stroke in the opposite direction. FIG. 1 illustrates a prior art configuration wherein a pawl 1 is pivotably positioned for engaging a bar or rack 2 having teeth 3. When rack 2 is moved relative to pawl 1, pawl 1 engages rack 2 against reverse movement until rack 2 has moved entirely past pawl 1, at which point pawl 1 pivots to a neutral position and return movement of rack 2 engages pawl 1 in the opposite position. As shown, pawl 1 is a single extending member pivotable around a single point spaced from the tooth engaging portion of pawl 1. This is disadvantageous in that there is a noticeable distance along which rack 2 must be moved relative to pawl 1 to allow sufficient space for pawl 1 to pivot into the proper position for ratcheting in the opposite direction. During this movement, pawl 1 and rack 2 are not engaged.
In addition, no positive structure is provided in this prior art device for insuring that the pawl is positioned in the proper position and will engage teeth 3 of rack 2 as desired.
Thus, it is clear that the need remains for a ratchet structure which is more reliable and has reduced or eliminated unengaged movement during the switchover from ratchet in one direction to ratchet in the other direction.
It is therefore the primary object of the present invention to provide a ratchet assembly which reliably provides two-directional ratcheting.
It is a further object of the present invention to provide a ratchet assembly which exhibits minimal unengaged movement during switchover from ratcheting in one direction to ratcheting in the other direction.
It is a still further object of the present invention to provide a surgical instrument including a ratchet assembly in accordance with the present invention.
It is another object of the present invention to provide a ratchet assembly and surgical instrument incorporating same which is simple in manufacture.
Other objects and advantages of the present invention will appear hereinbelow.